1. Field of the Invention
The present invention relates to a facsimile device for use in an ISDN (Integrated Services Digital Network), and a method of controlling the device.
2. Description of the Related Art
The ISDN provides different types of communication services such as a telephone communication, a data communication and a facsimile transmission, on a common digital network, and is constructed according to CCITT recommendations.
In the ISDN, a plurality of terminals can be connected to a single network termination (NT) device, and when a telephone number is called, all terminals having the same attribute as that of a calling terminal, among the terminals connected to the NT device corresponding to that telephone number, transmit "response" signals to the calling terminal, and the network allows one terminal which has responded earlier than other terminals to be called. Accordingly, the calling terminal cannot appoint a specific terminal as the called terminal.
To compensate for this shortcoming, the ISDN supports the use of subaddresses and dial-in services, to thus allow the calling terminal to specify the called terminal.
In conventional facsimile devices for use in the ISDN, when the facsimile devices receive a message including a valid subaddress, a facsimile device having the same subaddress as the received subaddress responds to the message, and then receives facsimile signals to record images on a recording paper. Nevertheless, when receiving a message not including the valid subaddress, the conventional facsimile devices respond unnecessarily to the calling message. Therefore, in the facsimile device connected to the ISDN, there arises a problem in that the recording paper is wasted when receiving unnecessary image data such as mischief data and direct mail data, etc.